signals and processing

Question 1

how does processing signals work

Answer 1

a signal is normally converted to a digital signal by sampling the input

analogue is converted to digital

Question 2

what is an anti-aliasing filter

Answer 2

a filter that eliminates frequencies that exceed a certain limit that is determined the sampling rate

Question 3

what is the sampling theorem

Answer 3

in order to recover a signal, the sampling rate must be greater than twice the highest frequency in the signal

Question 4

how are analogue quantities converted to digital form

Answer 4

• using a sample & hold circuit, the circuit samples the input signal at a rate determined by a clock signal and holds the level on a capacitor until the next clock pulse
• a positive half wave (0-10V) is shown in blue and the sample and hold circuit produces a staircase representation
• u
  quantise the staircase levels into binary coded form using an analogue to digital converter
• the digital values are then processed by a digital signal processor or a computer

Question 5

what is an operational amplifier

Answer 5

a linear amplifier that has two inputs and one output

(inverting and non-inverting)

Question 6

function of an operational amplifier

Answer 6

used as a comparator when 2 voltages are applied as inputs

Question 7

when is a op amp output HIGH

Answer 7

when the voltage on the +ve input is greater than the voltage on
the -ve input

Question 8

when is a op amp output LOW

Answer 8

when the -ve input voltage is greater than the +ve input voltage

Question 9

what is a flash ADC

Answer 9

a analogue to digital convertor that uses a series high speed comparators that compare the input with reference voltages